<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  <script src="../dev/vendors/vue.js"></script>
  <div id="example">
    <p>Original message: "{{ message }}"</p>
    <p>Computed reversed message: "{{ reversedMessage }}"</p>
  </div>
  <script>
    var vm = new Vue({
      el: '#example',
      data: {
        message: 'Hello'
      },
      computed: {
        // a computed getter
        reversedMessage: function () {
          // `this` points to the vm instance
          console.log('触发计算属性')
          return this.message.split('').reverse().join('')
        }
      }
      // methods: {
      //   reversedMessage: function () {
      //     return this.message.split('').reverse().join('')
      //   }
      // }
    })
  </script>

  <div id="demo">{{ fullName }}</div>

  <script>
    // var vm2 = new Vue({
    //   el: '#demo',
    //   data: {
    //     firstName: 'Foo',
    //     lastName: 'Bar',
    //     fullName: 'Foo Bar'
    //   },
    //   watch: {
    //     firstName: function (val) {
    //       this.fullName = val + ' ' + this.lastName
    //     },
    //     lastName: function (val) {
    //       this.fullName = this.firstName + ' ' + val
    //     }
    //   }
    // })
    var vm2 = new Vue({
      el: '#demo',
      data: {
        firstName: 'Foo',
        lastName: 'Bar'
      },
      computed: {
        fullName: {
          // getter
          get: function () {
            return this.firstName + ' ' + this.lastName
          },
          // setter
          set: function (newValue) {
            var names = newValue.split(' ')
            this.firstName = names[0]
            this.lastName = names[names.length - 1]
          }
        }
      }
    })
  </script>

  <div id="watch-example">
    <p>
      Ask a yes/no question:
      <input v-model="question">
    </p>
    <p>{{ answer }}</p>
  </div>
  <!-- Since there is already a rich ecosystem of ajax libraries    -->
  <!-- and collections of general-purpose utility methods, Vue core -->
  <!-- is able to remain small by not reinventing them. This also   -->
  <!-- gives you the freedom to just use what you're familiar with. -->
  <script src="https://unpkg.com/axios@0.12.0/dist/axios.min.js"></script>
  <script src="https://unpkg.com/lodash@4.13.1/lodash.min.js"></script>
  <script>
  var watchExampleVM = new Vue({
    el: '#watch-example',
    data: {
      question: '',
      answer: 'I cannot give you an answer until you ask a question!'
    },
    watch: {
      // 如果 question 发生改变，这个函数就会运行
      question: function (newQuestion) {
        this.answer = 'Waiting for you to stop typing...'
        this.getAnswer()
      }
    },
    methods: {
      // _.debounce 是一个通过 lodash 限制操作频率的函数。
      // 在这个例子中，我们希望限制访问yesno.wtf/api的频率
      // ajax请求直到用户输入完毕才会发出
      // 学习更多关于 _.debounce function (and its cousin
      // _.throttle), 参考: https://lodash.com/docs#debounce
      getAnswer: _.debounce(
        function () {
          var vm = this
          if (this.question.indexOf('?') === -1) {
            vm.answer = 'Questions usually contain a question mark. ;-)'
            return
          }
          vm.answer = 'Thinking...'
          axios.get('https://yesno.wtf/api')
            .then(function (response) {
              vm.answer = _.capitalize(response.data.answer)
            })
            .catch(function (error) {
              vm.answer = 'Error! Could not reach the API. ' + error
            })
        },
        // 这是我们为用户停止输入等待的毫秒数
        500
      )
    }
  })
  </script>
</body>
</html>